EVENT
BOARDSIZE 19
SETUP W D16 C13 C5 C4 D3 F3 S4 R7 R10 
SETUP B C11 D7 C6 D5 N3 Q4 Q16 O17 
MARK \t@S4
COM
Problem 64. Black to play.  

After White has played the marked stone, what should Black do
? 
ENDCOM
B 1 F17
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black should approach with 1.
ENDCOM
W 2 D17
COM
If White defends the corner with 2, ...
ENDCOM
  VAR
  W 2 K17
  MARK 1@F17
  COM
  Variation.

  White might pincer the black stone at 1 with 2.
  ENDCOM
  B 3 C17
  COM
  In that case, Black must take the corner territory with the sequence
  from 3 ...
  ENDCOM
  W 4 D17
  B 5 D18
  W 6 E18
  B 7 C18
  W 8 E17
  B 9 B15
  COM
  ... to 9. Black should be satisfied with this result.
  <=
  ENDCOM
  ENDVAR
B 3 K16
COM
... Black will extend to 3, making a moyo in the upper right.
<=
ENDCOM